The present invention relates to a method of and an apparatus for welding a pane with a space defined therein, and more particularly to a method of and an apparatus for welding inner and outer members of a side panel of an automobile, for example, with a welding gun while holding the inner and outer members with clamps, by welding the components of the outer members and welding the inner and outer members to each other in one welding station.
Side panels for automobiles are essentially composed of an outer member positioned on the outer side of an automobile body and an inner member positioned on the inner side of the automobile body. The outer and inner members of a side panel are welded together, with an inner space defined therebetween. The outer and inner side panel members are thus spaced from each other with the inner space therebetween because the side panel is required to have a certain thickness for a desired mechanical strength of its own and for supporting a door or the like.
The outer side panel member to be securely welded to the inner side panel member is manufactured in either of the two methods described below. According to the first method, an outer side panel member is produced as a unitary structure from a single pressed sheet material. According to the second method, a plurality of small separate elements or components are welded together into an outer side panel member. The latter process is widely employed in the art to produce outer side panel members since the material can be utilized to a great extent, and molds and presses are simple in structure.
For example, as shown in FIG. 1 of the accompanying drawings, an outer side panel member for a box-type automobile, e.g., a van, is composed of small components a through g. Before the components a through g are welded, they are positioned in abutment and fixed by clamps X. Thereafter, the components a through g are welded together at joints by welding guns Y.
Then, as shown in FIG. 2, small components h through k of an inner side panel member are positioned and fixed in superposing relation to the outer side panel member by clamps Xa, and are welded to the outer side panel member by welding guns Ya.
The small components are welded into the outer side panel member in a first welding station. The inner side panel member is then welded to the welded outer side panel member in a second welding station.
After the inner and outer side panel members are welded to each other an inner space is defined therebetween. If the outer side panel member were to be welded subsequently, a welding gun would not easily be brought into the inner space between the inner and outer side panel members. Therefore, it is necessary to weld the small components in advance to make up the outer side panel member.
The need for the two welding stations before a complete side panel is produced cannot be met if only a small factory space is available. Since workpieces have to be transferred from the first welding station to the second welding station, a suitable feed mechanism is necessary for such workpiece transfer. The first and second welding stations are required to have workpiece positioning clamps for positioning the side panel member components while they are being welded in the welding processes at the welding stations. As a result, the welding equipment in each of the welding stations is large in size and composed of many parts. The workpieces in the second welding station must be positioned with considerable accuracy because the workpieces tend to be displaced in position while they are being fed from the first welding station to the second welding station.